Some cave art is a marvel I hope to be able to see someday, one can dream?

I respect both your points, though I must admit I look at graffiti as a photographer.

Graffiti (singular: graffito; the plural is used as a mass noun) is writing or drawings scribbled, scratched, or sprayed illicitly on a wall or other surface in a public place.[1] Stickers and other adhesives are not considered graffiti. Graffiti ranges from simple written words to elaborate wall paintings, and has existed since ancient times, with examples dating back to Ancient Greece and the Roman Empire.
wikipedia